The present invention relates to photovoltaic solar cells and photovoltaic solar cell manufacturing. More particularly, the present invention provides a photovoltaic solar cell with an electroplated back side surface field and a back side electrical contact.
Photovoltaic solar cells, i.e., devices which convert photons from sunlight into electricity, are regarded as one of the key technologies which will lead to a sustainable energy future. In order for solar energy to be cost competitive and comparable with non-renewable sources of energy (such as, for example, oil, coal and natural gas), low cost processing and high efficiency solar cells are essential.
The majority (over 90%) of solar cells currently in production are based on silicon wafers with screen printed metal pastes as electrical contacts. Screen printing is attractive due to its simplicity in processing and high throughput capability; however, the high contact resistance, high paste cost, shadowing from wide conductive lines, high temperature processing, and mechanical yield loss are disadvantages that have not been overcome even after thirty plus years of research and development.
For advanced and experimental high efficiency solar cells, such as Sunpower's interdigitated, backcontacted solar cells, vacuum based metallization processes are used to avoid the disadvantages of screen printing. The high cost and low throughput of vacuum processes prohibit the implementation of these processes in single emitter solar cells, which types of solar cells are the majority in the current photovoltaic industry.